When starting a cold gas turbine engine, the temperature increases very rapidly in the outer section of its rotors. On the other hand, the temperature of the material around the central section of these rotors increases only gradually, generally through heat conduction so that a central section will only reach its maximum operating temperature after a relatively long running time. Meanwhile, the thermal gradients inside the rotors generate thermal stresses. These transient thermal stresses require that some of the most affected regions of the rotors be designed thicker or larger. The choice of material can also be influenced by these stresses, as well as the useful life of the rotors.
Overall, it is highly desirable to obtain a reduction of the transient thermal stresses in a rotor of a gas turbine engine because such reduction would have a positive impact on the useful life and/or the physical characteristics of the rotor, such as its weight, size or shape.